The shoot'em up Touhou Project games are fan-made PC games created by a one-man game studio. Touhou Project's creator, Zun, has been free-wheeling about derivative work—something that changed earlier this year.

Upcoming 2D arcade fighting game The King of Fighters XIII already has curvy ninja Mai Shiranui in its line-up. But just because KOFXIII has Mai, that doesn't mean the line-up is finalized. Two more fights are entering the fray.